Rotary granulator and dryer



I' 'July 5, 1966 I J. s, RAI-r1' 3,258,849

ROTARY GRANULATOR AND DRYER Filed April 2. 1963 vk/vrai da/y Suma/Farr ay l f rrmwfys United States Patent O 3,258,849 RGTARY GRANULATOR ANDDRYER John Stewart Raitt, Edinburgh, Scotland, assignor to ScottishAgricultural Industries Limited, Edinburgh, Scotland, a corporation ofGreat Britain Filed Apr. 2, 1963, Ser. No. 270,076 Claims priority,application Great Britain, Apr. 9, 1962, 13,538/ 62 8 Claims. (Cl.34-102) The present invention is concerned with improvements in orrelating to granulators.

The object of the invention is to provide a granulator of simplifiedconstruction which permits granules to be produced substantially by alayering process in a convenient and efficient manner.

According to the present invention a gr-anulator comprising a drumrotatable about a substantially horizontal axis is one wherein said drumcontains therein lifting means -attached at one end portion of the drumfor lifting therein and transferring therefrom solid material into astationary receiving and transferring means connected to an externalsupport and adapted to receive and transfer said solid material fromsaid end portion to the other end portion of the drum, wherein one endof the drum has an opening at least sufficiently wide for at leastconnecting means to pass therethrough from the receiving andtransferring means to said external support, and wherein the firstmentioned end portion has at least an opening for discharge of solidmaterial.

Preferably said lifting means comprises buckets or scoops fitted intothe drum so that on rotation of the granulator they lift the solidmaterial up and discharge it into said stationary receiving andtransferring means. The stationary receiving and transferring means ispreferably a stationary inclined chute. Preferably the opening fordischarge of solid material in the first mentioned end portion isconcentrically positioned at the end of this end portion so that itsdiameter controls the bed depth of the solid material, i.e. thegranules, in the drum.

Alternatively, said first mentioned end portion has a closed end and astationary plate adjacent to this closed end and said opening fordischarge of solid mate-rial is an aperture near the perimeter of saidclosed end and said stationary plate has a corresponding aperture in itslower segment which is in periodic alignment with the drum aperture andbed of solid material during rotation of the drum to permit discharge ofsolid lmaterial through said apertures.

If stationary means is provided to permit removal of gases and vapoursthis means is preferably fitted to a stationary plate adjacent to saidother end portion of the drum.

1f desired, external or internal means of heating or cooling areassociated with the granulator of the invention.

If the apparatus of the invention is to be used in a layering process,it is essential for etiicient granulation that the recycle ratio, whichis herein defined as the ratio of rate of recycle of material within thedrum to the rate of addition of material to be granulated, is kept aslarge as possible. Under equilibrium conditions the rate of addition ofmaterial to be granulated will be equivalent to the rate of removal ofmaterial from the granulator, Therefore, for a given production rate therecycle ratio is proportional to the rate of recycle of material withinthe drum. This recycle rate is a function of the number and size ofbuckets and scoops and the peripheral speed of the drum. It is knownthat this peripheral speed is limited to that range in which the bed ofmaterial moves substantially with a rolling action, which is desirablefor the said layering process. Preferably, it should be so arranged thatthe material discharged by the buckets or scoops forms a continuousstream in the said stationary transferring means. For example, if a 6cWt./hr. production rate is desired at a 55:1 recycle ratio, then thiscan be achieved in a 4 ft. 3 in. internal diameter drum rotating at 13r.p.m., thus having a peripheral speed of 173 ft./min., and fitted with16 buckets, each discharging 3 lbs. of material down the stationarytransferring means.

By way of example three embodiments of a granulator according to theinvention will now be described with reference to the accompanyingdiagrammatic drawings. Each drawing is a diametrally sectional elevationthrough the respective embodiment of a granulator, and lin FIGS. 1 to 3of the drawings similar parts of the grauulators are given the samereference numerals.

In FIG. 1 4a rotatable drum 1, of 4 ft. 3 in. internal diameter, open atboth ends 2 and 3, is mounted substantially horizontally. 4 is a chute,inclined at `an angle of 45 to the horizontal, which -is attached to`one end of la connecting rod 5, the other end of which is att-ached toa wall 6. 7 are lifting cups, sixteen in number, fitted in the dnum 1which, on rotation of drum 1, carry solid material 8 up until it dropsinto the chute 4. 'I'he opening at end 2 is wider than the opening atend 3, land is bounded by a lip 9 to retain the desired depth ofcirculating solid material -8 in drum 1. The two pipes 10 and 11 are forthe addition of liquids or gases, and each is fixed to the connectingrod 5. Pipe 10 is directed to the chute 4, and pipe 11 enters under thebed 8 of solid material.

In FIG. 2 a rotatable drum 12, open at both ends 13 and 14, is mountedsubstantially horizontally. At end 13 there is located a stationaryplate 15, which is attached to one end of a connecting rod 16, the otherend of which is attached to a Wall 17. This plate 15 -is fitted with aduct 18 for efiiuent gas removal, Vand with an outlet pipe 19, which-receives solid material from the bed 8 from lifting cups 20, four innumber, fitted to the drum 12.` 21 is an endless transport belt. Thedimensions of the dnum 12 are substantially the same as those of thedrum 1, illustrated in FIG. 1.

In FIG. 3 a rotatable drum 22, open :at end 23 and closed at end 24, ismounted substantially horizontally. A stationary plate 25 is located atclosed end 24. This plate 25 is fitted with a duct 26 for effluent gasremoval passing through a centrally positioned opening 27 through theclosed end 24. Plate 25 has also an orifice 28 in its lower segment.When these orifices 28 and 29, and the bed of solid material 8, are inperiodic [alignment during rotation of the drum 22, discharge of solidmaterial takes place through the orifice 28. The dimensions of the drum22 are substantially the same as those of the drum 1, illustrated inFIG. 1.

An :alternative method of discharge is to have a Weir, fixed oradjustable, not shown in FIG. 3, over which the material is allowed tospill out through orifice 28.

The apparatus of the invention has been found to be particularlyapplicable for the production of granular `ammonium nitrate, granularammonium sulphate, granular monoammonium phosphate and various metalmetaphosphates and sulphates in granular form.

For example, granular monoammonium phosphate is conveniently producedfrom wet-process phosphoric acid and gaseous ammonia in the reactorillustrate in FIG. 2 under the following conditions:

Concentration of acid 46.6% P205. Rate of rotation of drum 13 r.p.m.Rate `of recycle of material within the drum 330 cwt./hr. Productionrate 6.0 cwt./hr.

Percent of product size in solid discharge 72% Moisture content ofmaterial t discharged from granul-ator 0.31% H2O. Bed temperature 107 C.Moisture content of material at point of acid addition 0.51% H2O.`

What I claim is:

1. A granulator comprising: a drum rotatable about asubstantiallyhorizontal axis and having a discharge opening in one endportion for discharging solid material from said drum; lifting meansattached to the inner per-iphery of said drum at said one end portionfor lifting material from the bottom of said drum and subsequentlydropping the material during rotation of said drum; means for internallyrecycling material from said one end portion to said other end portion,said recycle means including lifting means attached to the innerperiphery of said dr-um at said one end portion for lifting materialfrom the bottom of said drum and subsequently dropping the materialduring rotation of said drum, said recycle means further includingstationary receiving and transferring means disposed within said drumfor receiving material dropped by said lifting means and for returningthe dropped material to said other end portion of said drum; astationary support exterior of said drum; and connecting meansinterconnecting said support, and said receiving and transferring meansfor positioning the latter in said drum. Y

2. A granulator as claimed in claim 1 including stationary duct meansfor removing gases from said one end portion, said duct means beingsupported by a stationary plate.

3. A graniilator as claimed in claim 1 including heat exchanger meansfor said drum.

4. A granulator as claimed in claim 1 wherein said lifting meanscomprises scoops.

5. A granulator as claimed in claim 1 wherein the stationary -receivingand transferring means isa stationary inclined chute.

6. A granulator as claimed in claim 1 wherein the opening for dischargeof solid materi-al is concentrically positioned at the end of said oneend portion.

7. A granulator as claimed in claim 1 wherein said one end portion has aclosed end and a stationary plate adjacent to this closed end, saidopening for discharge of solid material being an aperture near theperimeter of s-aid closed end and said stationary plate having acorresponding aperture in its lower segment which is in periodicalignment with the drum aperture during rotation of the drum.

8. A granulator comprising: a drum mounted for rotation about asubstantially horizontal axis, said drum having a discharge opening latone end for discharging solid material from said drum and -an inletopening at the other end, s-aid inlet opening being coaxial with saiddrum; two stationary inlet conduits extending into said other endthrough Said inlet open-ing; and means for internally recycling materialfrom said one end to said other end, s-aid recycle means includinglifting means attached to the inner periphery of said drum near said oneend for lifting solid material from the bottom of said drum andsubsequently dropping the material during rotation of said drum and astationary inclined chute wholly within said drum extending downwardlyfrom said one end to said other end for receiving solid material droppedby said lifting means and for transferring the material to said otherend.

References Cited by the Examiner UNITED STATES PATENTS 534,491 2/1895Atwood 34-136 X 582,587 5/1897 Hay 263-33 2,122,170 6/1938 Zotos 263--332,443,462: 6/1948 Kimberlin et al. 34-135 X 3,021,081 2/1962 Leader241-91 FOREIGN PATENTS 18,299 11/ 1904 Austria. 571,115 2/1933 Germany.814,182 6/1959 Great Britain.

FREDERICK L. MATTESON, JR., Primary Examiner.

WILLIAM F. ODEA, JOHN J. CAMBY, Examiners.

D. A. TAMBURRO, Assistant Examiner.

1. A GRANULATOR COMPRISING: A DRUM ROTATABLE ABOUT A SUBSTANTIALLYHORIZONTAL AXIS AND HAVING A DISCHARGE OPENING IN ONE END PORTION OFDISCHARGING SOLID MATERIALO FROM SAID DRUM; LIFTING MEANS ATTACHED TOTHE INNER PERIPHERY OF SAID DRUM AT SAID ONE END PORTION FOR LIFTINGMATERIAL FROM THE BOTTOM OF SAID DRUM AND SUBSEQUENTLY DROPPING THEMATERIAL DURING ROTATION OF SAID DRUM; MEANS FOR INTERNALLY RECYCLINGMATERIAL FROM SAID ONE END PORTION TO SAID OTHER END PORTION, SAIDRECYCLE MEANS INCLUDING LIFTING MEANS ATTACHED TO THE INNER PERIPHERY OFSAID DRUM AT SAID ONE END PORTION FOR LIFTING MATERIAL FROM THE BOTTOMOF SAID DRUM AND SUBSEQUENTLY DROPPING THE MATERIAL DURING ROTATION OFSAID DRUM, SAID RECYCLE MEANS FURTHER INCLUDING STATIONARY RECEIVING ANDTRANSFERRING MEANS DISPOSED WITHIN SAID DRUM FOR RECEIVING MATERIALDROPPED BY SAID LIFTING MEANS AND FOR RETURNING THE DROPPED MATERIAL TOSAID OTHER END PORTION OF SAID DRUM; A STATIONARY SUPPORT EXTERIOR OFSAID DRUM; AND CONNECTING MEANS INTERCONNECTING SAID SUPPORT, AND SAIDRECEIVING AND TRANSFERRING MEANS FOR POSITIONING THE LATTER IN SAIDDRUM.